Torque transmission device

ABSTRACT

A torque transmission device includes a shaft which has shaft teeth around its outer circumference, a hub which has hub teeth on an inner circumference, wherein the hub is arranged on the shaft in such a way that the shaft teeth and the hub teeth mesh with one another in order to transmit torque. The torque transmission device furthermore includes at least one spring element which passes entirely through the hub and is supported on the shaft and the hub and exerts a spring force on the hub and the shaft, wherein at least a component of the spring force is directed in such a way that around the entire circumference of the shaft and hub adjacent flanks of the shaft teeth and the hub teeth are pushed together.

The invention relates to a torque transmission device, in particular fora motor vehicle.

In motor vehicles it is required to transmit the torque produced by thedrive engine to the drive wheels. This torque transmitting operativecoupling is often referred to as drive train. Often, further componentssuch as a clutch, a transmission, differentials and wheel housings arecoupled to the drive engine on the output side. The transmission oftorques between rotating bodies is often accomplished by using so calledshaft-hub-connections, wherein materially bonding, form fitting orfriction fitting force transmission mechanisms are used. A form fittingforce transmission can for example be achieved by means of a reciprocaltoothing of the shaft and the hub. In this case the shaft has toothingson its outer circumference and the hub has toothings on the innercircumference, which engage in each other.

A disadvantage of these toothings is that due to the radial tolerancerequired for mounting, they tend to produce noise in certain operatingstates, which adversely affects driving comfort. This may also lead toincreased wear.

From DE 102006017167A1 braking elements for shaft-hub-connections areknown, which partially engage in the toothing from outside. Adisadvantage is here the complicated fastening of the braking elementson the shaft or hub.

From DE19855025A1 a suspension for a tooth clutch is known, which exertsa radial force onto the shaft and the hub in order to displace them outof their concentric position and to cause them to abut each other at twoopposing sites.

An object of the present invention is to provide a torque transmissiondevice which is characterized by a reduced noise development, a simplemounting and a cost effective construction.

This object is solved by the torque transmission device according to theindependent claim. Advantageous embodiments of the torque transmissiondevice are described in the dependent claims.

Claim 1 relates to a torque transmission device with a shaft, which hasa shaft toothing on its outer circumference, and a hub, which has a hubtoothing on its inner circumference. The hub is arranged on the shaft sothat the shaft toothing and the hub toothing engage in one another inorder to transmit a torque. The torque transmission device further hasat least one spring element which completely traverses the hub and issupported on the shaft and the hub and exerts a spring force on the huband the shaft, wherein at least one component of the spring force isoriented so that adjacent flanks of the shaft toothing and the hubtoothing are pressed against each other along the entire circumferenceof the shaft and the hub.

The invention is based on the idea to provide at least one springelement between the shaft and the hub, which is supported on the shaftand the hub and exerts a spring force on the shaft and the hub, whichcounteracts a rotation of the shaft and the hub relative to each otherand thereby suppresses this rotation to the most degree. As a result ofthe component of the force, which acts over the entire circumference ofthe shaft and the hub and is oriented in circumferential direction, therelative position of the shaft and the hub is stabilized in thedirection of rotation. The spring force has the effect that adjacenttooth flanks of the shaft toothing and the hub toothing come to restagainst each other over the entire circumference of the shaft and thehub. For this purpose the spring element has support sites on the toothflanks of the shaft toothing and/or the hub toothing. In this torquetransmission device, relative radial movements caused by the tolerancebetween shaft and hub, and with this undesired noise development andwear, are effectively prevented. The spring element does not primarilyserve the transmission of torques and is advantageously configured sothat it fixes the shaft and the hub in rotational direction, but not inaxial direction. For this, an axial compensatory movement between theshaft and the hub which may be required (for example due tomanufacturing tolerances or temperature differences between the shaftand the hub) is still possible.

in an embodiment of the torque transmission device according to claim 2the hub toothing and/or the shaft toothing has at least one gap, whereinthe spring element is arranged in the at least one gap.

The at least one gap of the corresponding toothing can be configuredcontinuous in axial direction (i.e., in direction of the rotational axisof the shaft). In the simplest case the omission of one tooth issufficient for the arrangement of the spring element. In the case ofmultiple spring elements corresponding gaps can be formed at any site ofthe toothing. Especially in the case of larger dimensioned springelements this creates sufficient space and facilitates mounting.

In an embodiment of the torque transmission device according to claim 3the at least on e spring element engages with its free ends behind thehub—in direction of the shaft rotational axis—on opposing front facessides of the hub.

In this way the spring element can be securely positioned in axialdirection, wherein a relative axial compensation of the shaft and thehub still remains possible.

In an embodiment of the torque transmission device according to claim 4at least one of the free ends of the spring element is fastened on anoutside of the hub.

The fastening can occur on an outside of the hub, which faces away fromthe inner toothing. For this a recess, a bore or a radial protrusion canbe formed on the outside of the hub, which is in form fitting engagementwith the spring element. This enables an even better securing of thespring element.

In an embodiment of the torque transmission device according to claim 5the at least one spring element engages with at least one of its freeends behind the shaft on a front side of the shaft.

In an embodiment of the torque transmission device according to claim 6at least one of the free ends of the spring element is fastened on theshaft.

These embodiments of the torque transmission device representalternative fastening options.

In an embodiment of the torque transmission device according to claim 7the spring element has two legs which—in circumferential direction ofthe shaft—are arranged at different positions, preferably opposingpositions, between the shaft and the hub.

For this, the spring element can be substantially bent U-shaped, thelegs extend preferably in the same direction. This embodiment of thespring may be a bent part made of spring wire, which can be producedeasily and cost effectively.

In an embodiment of the torque transmission device according to claim 8the coring element covers or engages behind hub on its side which facesaway from the legs on a front side of the hub at least in part.

In an embodiment of the torque transmission device according to claim 9,a free end of at least one leg can engage behind the hub on the opposingfront side.

In an embodiment of the torque transmission device according to claim 10the spring element engages axially around the shaft, wherein a free endof at least one leg is fastened on the shaft.

This constitutes a further alternative fastening option of the springelement.

In this case according to an embodiment of the torque transmissiondevice according to claim 11, the spring element can be configured sothat a radially outwardly acting force acts on the two legs.

This embodiment enables easy mounting and securement in axial directionof the spring element. In particular the radially acting spring tensionin connection with engagement of the free ends of the legs behind thefront side of the hub result in a type of clip mechanism.

In a torque transmission device according to claim 12 the at least onespring element is configured one-piece.

In particular the spring element can be an easily and cost-effectivelyproducible part made of spring steel with a flat or round cross section.

In the following, the invention is explained in more detail by way ofexemplary embodiments with reference to the included figures. In theFigures

FIGS. 1A and 2A are schematic representations of two embodiments of atorque transmission device;

FIGS. 1B and 2B are schematic representations of two embodiments of thespring element of the torque transmission device;

FIGS. 1C and 2C are schematic cross sectional view of the torquetransmission devices;

FIGS. 3A and 4A are schematic representations of two further embodimentsof a torque transmission device;

FIGS. 3B and 4B are representations of two further embodiment of thespring element of the torque transmission device;

FIGS. 1A and 2A schematically show two exemplary embodiments of a torquetransmission device 1. the torque transmission devices 1 haverespectively a shaft 2 with the rotation axis Z, a hub 3 and a sprigelement 4.

The exemplary embodiments of the FIGS. 1A, 1B and 1C differ from theexemplary embodiments of the FIGS. 2A, 2B and 2C only regarding theconfiguration of the respective spring element 4.

FIG. 1C or 2C are schematic cross sectional view of the torquetransmission devices of FIG. 1A or 2A taken along the sectional linesB-B or C-C.

FIGS. 3A, 3B, 4A and 4B show two further exemplary embodiments of atorque transmission device. These differ only with regard to the typeand shape of the used spring element.

As can be seen in FIGS. 1A, 2A and 1C, 2C, the hub 3 is arranged on theshaft 2. For this the hub 3 has a correspondingly dimensioned bore 5,with the shaft 2 being inserted with one end into the bore 5. In theexemplary embodiment the bore is a through bore. At least in the regionof the mutual overlap of the shaft 2 and the hub 3, the shaft 3 has atits outer circumference a shaft toothing 6 and the hub 2 has at itsinner circumference of the through bore 5 a hub toothing 7 (see FIGS. 1Cand 2C). The shaft toothing 6 and the hub toothing 7 engage with eachother for form fittingly transmitting a torque between each other (seeFIGS. 1C and 2C).

FIGS. 1B and 2B show schematic embodiments of the spring element 4 inthe free un-mounted state.

Both embodiments of the spring element 4 are configured one-piece andare advantageously made of spring-elastic material, for example springsteel. The spring elements 4 are cost-effectively producible with regardto the material as wells as manufacture. Any extrinsically effectedchange of shape, in particular a compression, extension or stretching ofthe spring element 4 causes a restoring force in the material of thespring element 4.

The embodiment of the spring element according to FIG. 1B has the shapeof a multiply bent spring rod, wherein an additional increased bent orshaping is imposed on the respective opposing free ends. As will becomeapparent from FIG. 1A the special shaping serves for fastening of thespring element 4 on the hub.

The embodiment of the spring element 4 according to FIG. 2B has two legs4-1, 4-2 with a common base 4-3. The main directions of extent of thelegs 4-1, 4-2 are the same and point in the same direction (in FIG. 2Btowards the left hand side).

The mounting, arrangement and function of the spring elements 4 are nowexplained by way of FIGS. 1A, 2A and 1C, 2C:

The spring elements 4 are mounted on the hub 3 prior to joining theshaft 2 and the hub 3.

In the embodiment of the spring element 4 according to FIG. 1B thespring element 4 is guided with a free end through the through bore 5 ofthe hub (see FIG. 1A). In the mounted state the spring element fullytraverses the hub, wherein the spring element 4 is shaped so that itengages behind opposing front sides 8, 9 of the hub 3 (i.e., the freeends abut a front side 8, 9 of the hub 3). A free end of the springelement can in addition be fastened on an outer side of the hub 3 whichfaces away from the through bore 5. In the exemplary embodiment of FIG.1A the bore 10 is arranged on the outside of the hub 3 into which thefree end of the spring element 4 is inserted. However, other shapes arealso conceivable in order to bring the free end in form fittingengagement with the hub.

Advantageously in the free state, i.e. in the relaxed state, the springelement 4 is shorter than the through bore, so that the spring element 4has to be slightly stretched for the mounting. As a result of thestretching a spring tension is built up in the spring element 4 which incombination with the ends which engage behind, ensures a secure fit ofthe spring element 4 in the hub.

In the embodiment of the spring element 4 according to FIG. 2B, thespring element is guided with both free legs 4-1, 4-2 through thethrough bore 5 of the hub 3 so that the spring element 4 completelytraverses the hub 4 (see FIG. 2A). The spring element 4 is configured sothat in the mounted state the base 4-3 of the spring element 4 covers orengages behind the hub 3 on the front side 9 or the spring element restsagainst a front side 9 of the hub. The two free ends of the legs 4-1,4-2 protrude out of the through bore 5 on the opposite side of the hub 3and engage behind the hub 3 on the opposing front side 8 (i.e., theyabut the front side of the hub 3).

Advantageously the spring element 4 according to the embodimentaccording to FIG. 2B is configured so that for the purpose of mountingin the hub 3 the two legs 4-1, 4-2 have to be pushed together. Inparticular the distance of the free ends of the legs 4-1, 4-2 is greaterthan the diameter of he through bore 5 of the hub 3. As a result thespring element 4 or the legs 4-1, 4-2 are radially outwardlypre-tensioned in the mounted state so that a radially outwardly actingforce acts on the spring element 4. This results in a better fit of thespring element 4 in the hub 3.

After mounting the respective spring element 4 on the hub 3, the shaft 2is pushed through the through bore 5 of the hub 3 so that the shafttoothing 6 and the hub toothing 7 come into engagement with each other.The spring element 4 is configured and dimensioned so that whenintroducing the shaft 2 in to the bore 5 of the hub the spring element4—more precisely the section inside the spring element situated in thethrough bore 5, is pushed radially outwardly. In the completely mountedstate of the torque transmission device 1 the spring element 4 isarranged between the shaft 2 and the hub 3 and is supported on thesupport sites A on the shaft 2 and on the hub 3. As a result of thedeformation of the spring element 4 during insertion of the shaft 2 intothe hub 3 a restoring material tension and spring force is established.

As can be recognized in FIGS. 1C and 2C, the spring element 4 issupported on the flanks of adjacent teeth of the shaft toothing. Asmentioned above the compression of the spring element 4 during theinsertion of the shaft 2 into the through opening of the hub 3 causes arestoring material tension and spring force F. As a result of thisarrangement at least one component of the spring force F is oriented ina circumferential direction or rotation direction of the shaft 2, i.e.,tangentially to the shaft 2 or the hub 3, and causes the flanks of theshaft toothing 6 and hub toothing 7 to be pushed together over theentire circumference. The force F or the corresponding component, actsover the entire circumference of the shaft 2 and hub 3 and is orientedtangentially to the shaft and hub over the entire circumference. Thespring force F thus acts over the entire circumference of shaft 2 andhub 3 against a possible relative rotation movement M of the shaft 2 andthe hub 3. As a result the position of the shaft 2 and hub 3 relative toeach other is fixed or stabilized and a striking of the flanks of theshaft toothing 6 and hub toothing against each other is at leastsignificantly reduced.

Even though only one spring element 4 is used in the embodimentaccording to FIG. 1B multiple spring elements 4 can also be arranged atdifferent angular positions in circumferential direction of the shaft 2and hub 3. This makes it possible that the relative position betweenshaft and 2 and hub 3 can be further stabilized and amanufacture-related tolerance in the toothing can be compensated.

For a simple mounting of the spring element 4 at least one gap 11 can beformed in the hub toothing 7 and/or the shaft toothing 6. For thispurpose for example a tooth may be omitted in the hub toothing 7 and/orthe shaft toothing 6.

A further advantage of the present invention is that even though theradial tolerance in the toothing 6, 7 of shaft 2 and hub 3 is reduced oreliminated (relative to the rotation axis Z of the shaft) an axialcompensation still remains possible. Further, for the mounting of thetorque transmission device, a relative alignment of shaft 2 and hub 3 inrotation direction is not required, i.e., the shaft 2 and hub 3 can beinserted into each other in any desired angular position (relative tothe rotation axis).

FIGS. 3A, 3B, 4A and 4B show alternative embodiments of the torquetransmission device 1. The differences reside in the shape and fasteningof the spring element 4 and in the mounting of the torque transmissiondevice 1. The principle functioning and the resulting advantages areidentical to the ones of the exemplary embodiments of FIGS. 1A, 1B and2A, 2B, 2C or are appreciated by a person with skill in the artanalogously, In the following only the differences are explained. Sameelements are provided with the same reference numerals.

For mounting of the exemplary embodiments of the torque transmissiondevice 1 according to FIGS. 3A and 4A, the corresponding spring elements4 (see FIGS. 3 b and 4B) are first arranged on the respective shaft 2.

When using the spring element according to FIG. 3B its free ends areinserted into correspondingly configured indentations 10 of the shaft 2,so that a form fitting connection of the shaft 2 results and the springelement 4 is securely fastened on the shaft 2. Advantageously the springelement 4 is dimensioned so that it has to be slightly stretched for themounting on the shaft, thus resulting in a pre-tension that additionallysupports the fastening. In the fastened state at least one free end ofthe spring element 4 engages behind the shaft 2 on a front side 10.However, it is also possible that both free ends of the spring element 4engage behind the shaft 2 on opposing front sides.

When using a spring element according to FIG. 4B the spring element isinserted with the free ends into correspondingly configured indentations10 on opposing outer sides of the shaft 2 so that a form fittingconnection with the shaft 2 results and the spring element 4 is securelyfastened on the shaft 2. Advantageously the spring element 4 isdimensioned so that the two legs 4-1, 4-2 have to be slightly pushedapart for the mounting so that additionally a pre-tension results whichsupports the fastening. In the fastened state the spring element 4engages around the shaft 2 with the legs 4-1, 4-2 and the base 4-3 on afront side 10 and the outer sides.

Subsequently in both exemplary embodiments, the hub 3 is pushed over theshaft 2 with the spring element 4 mounted thereon. The spring elements 4are dimensioned and configured so as to be slightly compressed alongtheir longitudinal extent and are supported on the shaft 2 and the hub 3on the support sites A. This results in a pre-tension in the springelement 4, which securely fixes the spring element between the shaft 2and the hub 3. At the same time this material tension generates a springforce F (analogous to FIGS. 1C and 2C), which counteracts a rotation ofthe shaft and the hub relative to each other. in contrast to theexemplary embodiments of FIGS. 1A, 1B, 1C and 2A, 2B, 2C the springelement is supported on the flanks of adjacent teeth of the hub toothing7.

What is claimed is: 1.-12. (canceled)
 13. A torque transmission device,comprising: a shaft having an outer circumference provided with a shafttoothing; a hub having an inner circumference provided with a hubtoothing, said hub being arranged on the shaft so that the shafttoothing and the hub toothing engage one another to transmit a torque;and at least one spring element completely traversing the hub and beingsupported on the shaft and the hub, said spring element exerting aspring force on the hub and the shaft, wherein at least one component ofthe spring force is oriented so that adjacent flanks of the shafttoothing and the hub toothing are pushed against each other over anentire circumference of the shaft and hub.
 14. The torque transmissiondevice of claim 13, wherein the hub toothing and/or the shaft toothinghave at least one gap, and wherein the spring element is arranged in theat least one gap.
 15. The torque transmission device of claim 13,wherein the at least one spring element has free ends which engage thehub behind opposing end faces of the hub.
 16. The torque transmissiondevice of claim 15, wherein at least one of the free ends of the springelement is fastened on an outside of the hub.
 17. The torquetransmission device of claim 13, wherein the at least one spring elementhas free ends, at least one of the free ends engaging the shaft behindan end face of the shaft.
 18. The torque transmission device of claim17, wherein the at least one free end of the spring element is fastenedon the shaft.
 19. The torque transmission device of claim 13, whereinthe spring element has two legs respectively arranged at differentpositions between the shaft and the hub.
 20. The torque transmissiondevice of claim 19, wherein the spring element at least partially coversthe hub on one of opposing end faces of the hub.
 21. The torquetransmission device of claim 20, wherein a free end of at least one ofthe two legs engages on another one of the opposing end faces of thehub.
 22. The torque transmission device of claim 19, wherein the springelement axially engages around the shaft and a free end of at least oneof the two legs is fastened on an outside of the shaft.
 23. The torquetransmission device of claim 19, wherein the spring element isconfigured so that a radially outwardly acting force acts on the twolegs.
 24. The torque transmission device of claim 13, wherein the atleast one spring element is configured one-piece.